What causes lower abdominal pain when bending?

I am so desperate for answers for my mother. I am a medical school student but I can't seem to pinpoint anything for her. She has had abdominal pain, especially when bending, for a couple of years now. When it became severe at the beginning of this year she went to the doctor and ended up having a hysterectomy. This has not helped at all. As soon as she recovered and stop taking post op pain meds the fierce pain returned. I should mention that she's had a normal CT scan (although I can't be sure it was properly read/interpreted). Also should mention that pain is somewhat relieved with a BM. If you this sounds familiar and you or someone you know has the same situation and have received a correct diagnosis PLEASE give me some ideas. The last thing I want is for doctors to give up and stick her with some cop-out diagnosis like "IBS" (though I realize that could be the correct diagnosis for some cases). She is not stressed and she certainly isn't a hypochondriac. Something's wrong and I'd appreciate any attempt to help me get the right answer. ANY idea is welcomed. Thanks!